1. Field of the Invention
The present invention relates to an organic light emitting diode (OLED) display device and a method of manufacturing the same, and more particularly, to an active-matrix OLED (AMOLED) display device and a method of manufacturing the same.
2. Discussion of the Related Art
Recently, as the information age has come and research on flat panel display devices continues to accelerate, OLED display devices posterior to liquid crystal display (LCD) devices are being actively developed as next-generation flat panel display devices.
Since OLED display devices are self-emitting devices, the OLED display devices do not need a backlight unlike LCD devices, and thus can be more lightened and thinned than the LCD devices. Also, the OLED display devices are driven at a low voltage, realize colors close to natural colors, and have high emission efficiency, a wide viewing angle, and a fast response time. Accordingly, the OLED display devices can vividly realize high-quality moving images.
OLED display devices are current driving devices, and use a complicated driving circuit compared to LCD devices. In each of a plurality of sub-pixels defined by intersection between a plurality of gate lines and data lines, a gate signal transferred through a gate line is applied to a gate electrode of a switching thin film transistor, and a data signal transferred through a data line is applied to a driving thin film transistor by the gate electrode. The data signal applied to a gate electrode of the driving thin film transistor allows a driving current transferred through a power source line to be applied to an anode electrode of a corresponding sub-pixel, thereby driving an organic light emitting layer.
As described above, each sub-pixel of an OLED display device includes a switching thin film transistor and a driving thin film transistor, namely, fundamentally needs two or more thin film transistors. Also, each sub-pixel includes a complicated compensation circuit, for emitting desired color light during a desired time.
The aperture ratio of OLED display devices is considerably lowered by the thin film transistors and the compensation circuit, and thus the intensity of light emitted to the outside is reduced, and light extraction efficiency decreases.
Moreover, light emitted from an OLED of an OLED display device passes through a plurality of thin films, and is finally transferred to the outside through a polarizer. The polarizer is applied to OLED display devices, for preventing the reflection of external light. The emitted light is totally reflected by the thin films and thus lost, or at least 50% of the emitted light is lost while the emitted light passes through the polarizer. For this reason, luminance and light extraction efficiency are reduced.